This invention relates to a rotary piston compressor and refrigerating equipment; and, more particularly, the invention is directed to a rotary piston compressor in which a rotor and a vane are unitarily formed, and to refrigerating equipment using the rotary piston compressor, such as an air conditioner, a refrigerator, and a refrigerating device.
A conventional rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston unitarily has a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber.
The vane is extended into the bushing housing chamber, so that the rotary bushing is divided into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane.
In the rotary piston compressor, the rotary bushing rotates in the bushing housing chamber with the rotation of the roller to absorb rotation and axial motion of the vane, thereby increasing the volume of the suction chamber and decreasing the volume of the compression chamber. In this manner the refrigerant is drawn into the suction chamber and compressed in the compression chamber, being discharged out of the cylinder.
A prior art rotary piston compressor has been disclosed in, for instance, JP-A No. H7-158574.
The prior art rotary piston compressor, however, has a drawback in that, when drawn into the cylinder chamber immediately after starting, a liquid refrigerant or a wet refrigerant is subject to volume expansion the instant when the refrigerant is drawn into the cylinder chamber, or to volume contraction when the refrigerant is still in an almost liquid state. Since, in this case, the rotary piston roller and vane are unitarily formed, the refrigerant is likely to be excessively compressed.
Therefore, it has been proposed to form a dead space communicating with the compression chamber, whereby transient overcompression occurring at the time of starting will be alleviated. However, during routine operation, the presence of the dead space allows a high-pressure gas to remain within the cylinder chamber after the end of the discharge stroke, causing re-expansion of the refrigerant in the following stroke and accordingly resulting in a pressure loss at the time of suction and a lowering of the refrigerating capacity.
It is therefore an object of this invention to provide a reliable, high-performance rotary piston compressor and refrigerating equipment which are of a simple configuration and are capable of preventing overcompression without deterioration of performance during routine operation, and which are also capable of preventing re-expansion of the refrigerant after the completion of the discharge process.
For attaining the above-described object, according to a first feature of this invention, a rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston is unitarily formed with a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber. The vane is extended into the bushing housing chamber, so that the rotary bushing is separated into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane. The rotary bushing on the compression chamber side is disposed so as to move away from the cylinder chamber when the compression chamber pressure has been not less than a specific pressure, and also to move toward the cylinder chamber when the compression chamber pressure has decreased to not more than a specific pressure. With the movement of the rotary bushing on the compression chamber side, a communicating passage for communication between the compression chamber and the space on the discharge side outside of the cylinder is opened and closed.
According to a second feature of this invention, the rotary bushing on the compression chamber side has a portion facing the compression chamber and a portion facing the high discharge pressure side, and is so arranged as to move away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the high discharge pressure side is not less than the specific value, and to move toward the cylinder chamber when the resultant has decreased to not more than the specific value. The communicating passage for communication between the compression chamber and the space on the discharge side outside of the cylinder therefore is opened and closed with the movement of the rotary bushing on the compression chamber side.
According to a third feature of this invention, the rotary piston compressor is provided with a cylinder including a cylinder chamber, a bushing housing chamber connected to the cylinder chamber, and a oil-supply pump chamber connected to the bushing housing chamber. The oil-supply pump chamber communicates with the high discharge pressure side; the vane is extended from the bushing housing chamber to the oil-supply pump chamber, which therefore is provided with the pumping function by the motion of the vane; the rotary bushing on the compression chamber side has a portion facing the compression chamber and a portion facing the oil-supply pump chamber, and moves away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the oil-supply pump chamber is not less than a specific value, and moves toward the cylinder chamber when the resultant has decreased to not more than the specific value.
According to a fourth feature of this invention, the compression chamber side of the bushing housing bore which forms the cylinder chamber is comprised of a circular portion on the cylinder chamber side, an intermediate straight portion, and a circular portion on the opposite side of the cylinder chamber as viewed from the vicinity of the cylinder chamber.
According to a fifth feature of this invention, the bushing housing bore defining the cylinder chamber asymmetrically forms the suction chamber side and the compression chamber side. The rotary bushing on the suction chamber side is so formed as to have approximately the same external semicircular shape as the semicircular portion on the suction chamber side of the bushing housing bore.
A sixth feature of this invention resides in the fact that the intermediate straight portion spreads outward.
A seventh feature of this invention resides in the fact that the rotary bushing on the compression chamber side moves away from the cylinder chamber when the compression chamber pressure has been not less than the specific pressure in the discharge stroke of the compressor, and moves toward the cylinder chamber when the compression chamber pressure has lowered to not more than the specific pressure after the completion of the discharge process of the compressor.
An eighth feature of this invention resides in the fact that a refrigerating cycle is formed by connecting a rotary piston compressor, a condenser, a pressure reducing device, an evaporator, and a receiver tank by means of a piping. The rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston unitarily has a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber. The suction chamber is connected to a piping from the receiver tank. The vane is extended into the bushing housing chamber. The rotary bushing is so arranged as to be separated into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane. Furthermore, the rotary bushing has a portion facing the compression chamber and a portion facing the high discharge pressure side, and is so arranged as to move away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the high discharge pressure side has been not less than a specific value, and to move toward the cylinder chamber when the resultant has decreased to not more than the specific value. The communicating passage for providing communication between the compression chamber and the space on the discharge side outside of the cylinder therefore is opened and closed with the movement of the rotary bushing on the compression chamber side.
According to a ninth feature of this invention, a refrigerating cycle is formed by connecting a rotary piston compressor, a condenser, a pressure reducing device, an evaporator, and a receiver tank by means of a piping. The rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The compression chamber side of the bushing housing bore defining the cylinder chamber is comprised of a circular portion on the cylinder chamber side, an intermediate straight portion, and a circular portion on the opposite side of the cylinder chamber as viewed from the vicinity of the cylinder chamber; the intermediate straight portion being designed to spread outward.
Other objects, features and advantages of this invention will be apparent from the following detailed description taken in connection with the accompanying drawings.